The present invention relates generally to a printing apparatus for producing images on card substrates such as driver's licenses, employee badges, student cards, and the like. More particularly, the invention relates to a card-cleaning assembly for use in card printers, particularly thermal card printers. The assembly includes a card-cleaning roller and adhesive tape cartridge.
There are various known card printing apparatus which use a thermal printing process for producing colored images on card materials. In general, these printing devices use a conventional thermal dye transfer printing method, wherein a thermal printing head thermally-transfers dyes from a dye ribbon to a surface of the card. The thermal dye is transferred to and absorbed by the card's surface via a diffusion mechanism.
The thermal dye ribbon contains thermal dye panels of different colors, typically cyan (C), magenta (M), and yellow (Y), which are arranged in a repeating pattern. The dye ribbon may contain a black thermal dye panel (K) if desired. The colored panels may be arranged in an arbitrary order, or in a specific sequence that repeats itself along the ribbon. Typically, the colored panels are arranged in a CMYK color pattern. The printer can produce a full-colored image on the card's surface by combining the three primary colors. Generally, the card must make three separate passes under the print head (i.e., one pass for each color) in order to produce such a full-colored image.
Thus, in one type of thermal printer, the card is placed on a guided carriage or truck which moves forward on guide rails and transports the card to a position under the thermal print head. At this point, the first dye (for example, cyan) is thermally transferred to the dye-receptive surface of the card. After the card has been printed with the first dye, the carriage holding the card moves rearward and returns the card to a print-starting position. The dye transfer ribbon is advanced so that the second dye panel (for example, magenta) is in position, and the carriage again moves forward to a location under the print head. At this point, the second dye is transferred onto the card's surface. The second dye overlays the printed pattern formed by the first dye. Then, the card is returned to the print-starting position. Finally, the dye transfer ribbon is advanced again so that the third dye panel (for example, yellow) is in position, and the carriage again moves forward to a location under the print head. Then, the card which has been printed with the first and second dyes is further printed with the third dye to produce the full-colored image.
One problem with conventional thermal printers and thermal printing processes is the contamination and soiling of card substrates. The cards can be contaminated in a number of ways. For example, the card substrates typically are produced by cutting plastic sheets into the desired card shapes. This cutting operation can leave plastic shavings in the card packaging. Also, once the cards are removed from their packages, they are susceptible to air-borne contaminants such as dirt and dust particles. When the cover of the thermal printer is open, debris can fall into the printer and land on the cards. Air is circulated within printers, and this air can blow foreign matter onto the surfaces of the cards.
Card contamination creates several problems. For example, if the image is printed on a card surface loaded with dust and dirt particles and these particles fall off before lamination of the card, then the image under the particles may be lost. If the particles remain adhered to the surface, then defects may appear in the image, and the print quality may be poor. Further, the thermal print head is optimized to print on certain types of card stock. If the dust and dirt particles are large enough, they can cover the active elements of the print head and prevent these elements from transferring dye to the surface of the card. The dust and dirt particles can also damage the elements of the print head so that even after the element is cleaned, it will not transfer dye. Finally, a laminate is adhered to the card after the card is printed with an image. Contaminates trapped between the card and the laminate film will create bubbles that reduce the overall quality of the printed card.
The industry has attempted to address this problem by various means. For example, Morgavi, U.S. Pat. No. 5,536,328 discloses a cleaning card for a thermal card-printing machine having a station where the cards are electrically customized by means of a landing contact. According to the '328 Patent, the cleaning card has dimensions substantially identical to those of the cards to be printed. Further, the cleaning card is coated with two cleaning flat pads. One cleaning pad is coated with an adhesive material for collecting dust and dirt from the rollers in the machine. The other cleaning pad is coated with a material, such as abrasive paper, for cleaning the electrical contacts.
Nubson et al., U.S. Pat. No. 5,401,111 discloses an apparatus system for cleaning plastic cards such as credit or bank cards. According to the '111 Patent, the system can be used with thermal printers. The apparatus includes a pair of cleaning rollers which engage both sides of the card. The cleaning rollers have an adhesive coating for removing loose particulate matter from both sides of the card. The apparatus also includes an adhesive tape assembly for stripping the collected particulate matter away from the cleaning rollers. The surface of the adhesive tape is more adhesive than the surface of the cleaning rollers.
Nardone et al., U.S. Pat. Nos. 5,673,076, 5,667,316, and 5,966,160 disclose a card printing apparatus containing a silicone roller for removing dirt and dust particles from the surface of the card. An adhesive tape is used to clean the silicone roller. The tape lifts and collects the dirt and dust particles from the silicone roller. The Patents describe a tape assembly including a tape supply roll, tape take-up roll, and pivot arm. The adhesive cleaning tape is wound off the supply roll, around the pivot arm, and onto the take-up roller. This winding path produces tension in the tape and causes the pivot arm to pivot, thereby moving the tape into engagement with the silicone roller. The adhesive tape removes the dirt and dust particles from the roller as the roller rotates. The tape becomes disengaged from the silicone roller after the roller makes a complete revolution.
Although the tape assembly described in the '076, '316, and '160 Patents is effective in removing dirt and dust particles from the silicone roller, the assembly has some disadvantageous features. Particularly, the cleaning tape must be wound from a supply roll and around a pivot arm, and onto a take-up roller. It can be difficult and time-consuming to replace the cleaning tape, since the tape must be threaded along this complex path in each instance. Further, the tape can rip or jam during the cleaning process.
In view of the foregoing, it would be desirable to have a card-cleaning assembly that can be installed and removed easily from the thermal printer. One objective of the present invention is to provide such a card-cleaning assembly. Further, the cleaning assembly should be capable of dispensing the adhesive tape efficiently to remove dirt and dust particles and other debris from the card-cleaning roller. The present invention provides such a cleaning assembly. These and other objects, features, and advantages of this invention are evident from the following description and attached figures.